Post-tetanic potentiation in the innervated smooth muscle preparation of the guinea-pig ileum.

The phenomenon of posttetanic potentiation of electrically evoked twitch contractions in the myenteric plexus-longitudinal muscle of the guinea-pig ileum was observed when (1) post-tetanic inhibition had been prevented by naloxone, an opiate receptor antagonist, and (2) the twitches had been diminished by indomethacin, an inhibitor of prostaglandin synthesis. The origin of posttetanic potentiation at this muscarinic synapse appeared to be presynaptic.